karthikeid
- Dec 7, 2008
- 94
- Joined
- Dec 7, 2008
- Messages
- 94
hi
ok chill hero999...
why i am asking is that i have those components with me so that is why i was asking about that circuit....kindly help me out to do this circuit....
i cant get LM2931A...is there any substitute ???
ok chill hero999...
why i am asking is that i have those components with me so that is why i was asking about that circuit....kindly help me out to do this circuit....
i cant get LM2931A...is there any substitute ???
Last edited by a moderator:
audioguru2
- Apr 6, 2004
- 12,026
- Joined
- Apr 6, 2004
- Messages
- 12,026
The simple FM transmitter circuit has its tuned circuit connected to its antenna which causes its frequency to change if something moves near the antenna.
It does not have a voltage regulator so its frequency also changes as the battery voltage runs down.
It does not have pre-emphasis like all FM radio stations have so it will sound muffled like your stereo with its treble tone control turned all the way down.
The LM2931 is a 5V low-dropout regulator. All semiconductor manufacturers make some.
The 78L05 fails when the battery voltage is less than 7V. A 5V low dropout regulator still works perfectly when the battery voltage has dropped to 5.5V.
It does not have a voltage regulator so its frequency also changes as the battery voltage runs down.
It does not have pre-emphasis like all FM radio stations have so it will sound muffled like your stereo with its treble tone control turned all the way down.
The LM2931 is a 5V low-dropout regulator. All semiconductor manufacturers make some.
The 78L05 fails when the battery voltage is less than 7V. A 5V low dropout regulator still works perfectly when the battery voltage has dropped to 5.5V.
while considering LDO regulator with 9V battery, i fear the reason that even if the battery comes to 6V or so, LM2951 would regulate-- is not justified. A 9V battery discharged till 6V can't deliver any useful load. thus 5.2 as Input from a 9V battery imagining to serve the circuit can well be forgotten
True a 9V battery with an open circuit voltage of 6V can't produce much current, however when the regulator is connected the open circuit voltage is unimportant. For example, suppose the battery is discharged to the point where its open circuit voltage is 7V but when you connect the transmitter, the voltage drops to 6V; if you were using an LM7805, the voltage to the oscillator will drop below 5V causing it to drift but if you used a LDO regulator, it would stay at 5V.
Last edited by a moderator:
audioguru2
- Apr 6, 2004
- 12,026
- Joined
- Apr 6, 2004
- Messages
- 12,026
Look at the graph of voltage and discharge time for an Energizer 9V alkaline battery at a load of 53mA (my FM transmitter's current).
In about 2.5 hours the voltage drops to 7V where a 78L05 fails to regulate. But it still can power a low dropout regulator for an additional 11.5 hours.
View attachment 40610
In about 2.5 hours the voltage drops to 7V where a 78L05 fails to regulate. But it still can power a low dropout regulator for an additional 11.5 hours.
View attachment 40610
karthikeid
- Dec 7, 2008
- 94
- Joined
- Dec 7, 2008
- Messages
- 94
is there any other substitute to overcome this ???
Ideally you need a 5V regulator with a drop-out voltage <1V@50mA will do.
As I said before you could use the LM7805 which has a typical drop-out of 1.5V@50mA but the battery will only last for about 8 hours.
You can buy the LM2931AZ-5 from Futurlec which is based in Thailand and ship globally.
http://www.futurlec.com/Linear/LM2931AZ-5pr.shtml
After that point of reaching 7V, I doubt that the said battery would have have capacity to drive the output transistor , through it might still drive the small needs of the LDO output load.
I got a question here: There are commercial FM-transmitters (e.g. from Apple) which send a few meters.
I'd like to build such one and don't want to bother others on the highway by hearing crazy music from my ipod in my oldschool car radio
Does somebody know about a schematic to this kinda FM-transmitter?
This transmitter looks nice to me because of the easy way to build inductors http://w1.859.telia.com/~u85920178/tx/bug5.htm
but up to 1km range is quite a bit too good for me
Sry for my English
Greets, Br4in
I'd like to build such one and don't want to bother others on the highway by hearing crazy music from my ipod in my oldschool car radio
Does somebody know about a schematic to this kinda FM-transmitter?
This transmitter looks nice to me because of the easy way to build inductors
http://w1.859.telia.com/~u85920178/tx/bug5.htmbut up to 1km range is quite a bit too good for me
Sry for my English
Greets, Br4in
audioguru2
- Apr 6, 2004
- 12,026
- Joined
- Apr 6, 2004
- Messages
- 12,026
The modern FM stereo transmitters made for transmitting an MP3 to your car radio have an attenuator at their antenna to reduce their range. You might be able to remove or to bypass the attenuator.
The lousy old BA1404 FM stereo transmitter IC had terrible performance so it was replaced about 10 years ago by the modern ones (BH141x) that work extremely well.
Silicon Chip magazine had a project about The Micromitter that uses the BH1417 IC. It is a kit in Australia. Look at the line of ICs at www.rohm.com .
Here is the Micromitter project:
http://electronics-diy.com/schematics/BH1417_fm_transmitter.htm
The lousy old BA1404 FM stereo transmitter IC had terrible performance so it was replaced about 10 years ago by the modern ones (BH141x) that work extremely well.
Silicon Chip magazine had a project about The Micromitter that uses the BH1417 IC. It is a kit in Australia. Look at the line of ICs at www.rohm.com .
Here is the Micromitter project:
http://electronics-diy.com/schematics/BH1417_fm_transmitter.htm
Last edited by a moderator:
Well, I'm interested in making one myself @Sasi, but to be honest the Micromitter project posted by audioguru is way too big for me...
Is there a way to make an easier transmitter which works fine, or rather is the BA1404 really as bad as you say, audioguru?
Thx for your help!
Is there a way to make an easier transmitter which works fine, or rather is the BA1404 really as bad as you say, audioguru?
Thx for your help!
audioguru2
- Apr 6, 2004
- 12,026
- Joined
- Apr 6, 2004
- Messages
- 12,026
The BA1404 is obsolete. It has not been made for 10 years. Where will you buy one? But some kits still use it.
There are reviews about it on the web. Don Lancaster says it was a terrible transmitter that drifts its frequency so much that a modern digital tuner cannot receive it. Another review say its stereo separation was poor and its 19kHz pilot is a square-wave with many harmonics that causes whistling noises. It has hiss. It has severe distortion. In the 80's (yes, 25 years ago) it was the only FM stereo transmitter IC available.
karthikeid
- Dec 7, 2008
- 94
- Joined
- Dec 7, 2008
- Messages
- 94
hi
how to add an condenser mic to this circuit is this circuit transmit well ???
ur opinion pls...
View attachment 40666
how to add an condenser mic to this circuit is this circuit transmit well ???
ur opinion pls...
View attachment 40666
audioguru2
- Apr 6, 2004
- 12,026
- Joined
- Apr 6, 2004
- Messages
- 12,026
A condenser mic needs a 48V supply. Instead, why not use an inexpensive electret mic that has the 48V built-in? The electret mic meeds to be powered through a 10k resistor from a voltage of 3V to 12V that is filtered.
The simple transmitter circuit needs to have an electret mic preamp circuit for a mic to be used.
The simple circuit will sound bad because it is missing pre-emphasis that all FM radio stations have. The de-emphasis in all FM radios will sound like your stereo with its treble tone control turned all the way down.
The simple transmitter circuit needs to have an electret mic preamp circuit for a mic to be used.
The simple circuit will sound bad because it is missing pre-emphasis that all FM radio stations have. The de-emphasis in all FM radios will sound like your stereo with its treble tone control turned all the way down.
Similar threads
